#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: G171117 JieJiSS

def f_in(prompt=""):
    r"""
    float(input(...))
    """
    return float(input(prompt))

R1 = f_in("请输入R1阻值：")
R2 = f_in("请输入R2阻值：")
print("并联阻值为", R1 * R2 / (R1 + R2), sep='')
